1. Field of the Invention
The present invention relates to a liquid crystal television apparatus, and more specifically, to arrangement of circuits on a board.
2. Description of the Related Art
Recently, a liquid crystal television apparatus employing an LCD (liquid crystal display) as a display (hereinafter abbreviated as liquid crystal television) have widely spread. The liquid crystal television has an advantage of thinness, light-weight and low power consumption as compared with a conventional television employing a CRT (cathode ray tube). Typically, the liquid crystal television contains a light source for backlight. In such a liquid crystal television, a color image is displayed on a screen of liquid crystal cells by irradiating light emitted from the light source on liquid crystal cells in front of the light source through a diffusion plate or a prism sheet and passing the light through color filters provided in the cells.
FIG. 3 shows an electric block diagram of a general liquid crystal television. Reference numeral 21 denotes an antenna for receiving broadcasting electromagnetic wave signals and reference numeral 22 denotes a tuner for extracting an image signal having a selected frequency from the signals received in the antenna 21. Reference numeral 23 denotes a signal processor for performing a digital processing for the image signal extracted by the tuner 22. The signal processor 23 includes one digital IC containing a CPU, a video decoder for decoding the image signal, a timing controller for controlling display of images, etc.
Reference numeral 24 denotes known liquid crystal cells in which images are displayed on the basis of outputs from the signal processor 23. Source drivers 31 to 35 and gate drivers 36 and 37 are attached to the liquid crystal cells 24. Each of the source drivers 31 to 35 is a circuit for driving pixels (R, G, B) in an X direction (horizontal direction) of the liquid crystal cells 24 and each of the gate drivers 36 and 37 is a circuit for driving pixels in a Y direction (vertical direction) of the liquid crystal cells 24. Each of these drivers includes one IC and is supplied with output signals from the signal processor 23. In addition, the ICs forming the gate drivers 36 and 37 are mounted on a glass substrate of the liquid crystal cells 24, and also, wires carrying the output signals from the signal processor 23 are provided on the glass substrate.
Reference numeral 25 denotes a backlight unit arranged at a back side of the liquid crystal cells 24. The backlight unit 25 includes light sources 26a and 26b for backlight for irradiating the liquid crystal cells 24. The light sources 26a and 26b for backlight are cold cathode tube, for example. Reference numeral 27 denotes a power supply for supplying voltages required for various components based on a voltage of AC 100V obtained through a power plug 28. Reference numeral 29 denotes an inverter for supplying a voltage required to drive the light sources 26a and 26b for backlight to the backlight unit 25.
In FIG. 3, blocks of components related to voice are not shown for the purpose of brevity. Also, a microcomputer, a memory and the other components forming a controller are not shown for the purpose of brevity.
In the above-configured liquid crystal television, the tuner 22, the signal processor 23, the power supply 27, and the inverter 29 are mounted on a circuit board contained in a body of the television. A television circuit board on which a tuner, a signal processor, a power supply and the other components are mounted, is disclosed in JP-A-6-334543 (paragraph [0024] to [0028], and FIG. 2). Also, arrangement of connection lands at a portion in which the tuner on the circuit board is mounted, is disclosed in JP-A-2002-217765 (paragraph [0012] to [0028]).
Since a digital signal process is performed in a liquid crystal television, various circuit components for the digital signal process are needed and a multilayered board is requisite to improve efficiency of board packaging. Accordingly, a multilayered board, for example, a four-layered board, on which the tuner, the signal processor, the power supply, the inverter and the other components are integrally mounted, has been conventionally used as the circuit board of the liquid crystal television. However, such a multilayered board is expensive, which is a great obstacle to cost-down of the liquid crystal television. On the other hand, when a single-sided board is used instead of the multilayered board in the liquid crystal television, a great mounting area is needed, which may allows the board impossible to be contained in the liquid crystal television since there exist many circuit components in the liquid crystal television, as mentioned above, although the single-sided board is less expensive than the multilayered board.
In addition, since the single-sided board has low flexibility for a wiring pattern such as a power line or a ground line, as compared to the multilayered board, there arises a problem in that circuits on the board are susceptible to noises depending on arrangement of the circuits on the board and characteristics of the circuits are deteriorated. For example, when the tuner is arranged adjacent to the power supply as disclosed in JP-A-6-334543, noises generated in the power supply overlaps with a signal from the tuner and are transmitted to the signal processor, which results in deterioration of image quality due to noises appearing on a screen of the television.